A bridge joins two things together. An island to the main land. The shores of a river. The two sides of a canyon.
As a spiritual symbol, it usually represents a bridge between heaven and earth. In Christianity, it could represent Christ as that bridge or it could represent teaching that help us get to heaven. This bridge is often difficult to cross. It may be guarded by a beast such as a dragon. It is said that now it can be crossed only in death or by solar mystics in an enlightened state. It can also be a razors edged bridge indicating the difficulty of crossing by maintaining a balance between the two worlds of spirit and matter. The rainbow is often used as a symbol for this bridge. The “pot of gold” at the end of this rainbow is not metal coins but spiritual enlightenment.
It may also be depicted as stairs or a ladder.